Modeling Examples Demonstrating Reduction in Fatigue

Results

All presentations show basically the same benefits for the teetering hub in comparison to the rigid hub.  They show the following:

1. Significant reduction in the bending torque applied to the tip of the main shaft (LSSTipMya and LSSTipMza).

2. Significant reduction in the torque applied to the main shaft bearing (LSSGagMys and LSSGagMzs).

3. Significant reduction in the cyclic variability in out-of-plane shear force applied to the blade root (RootFxc1, RootFxc2 and RootFxc3). 

4. Significant reduction in the cyclic variability in out-of-plane torque applied to the blade root (RootMyc1, RootMyc2 and RootMyc3).  Very similar results are seen with the blade flapwise moment (RootMyb1,  RootMyb2 and RootMyb3).

5. Significant reduction in the cyclic variation in out-of-plane bending of the shaft tip (OoPDefl1, OoPDefl2 and OoPDefl3).

6. Significant reduction in the yaw bearing pitch and yaw moments (YawBrMyp and YawBrMzp).

Modeling comparison of the rigid and teetering two-bladed AWT-27 wind turbines shows comparable results to the three bladed comparison. One exception is that there is little difference between LSSTipMza for the rigid and teetering configurations. This is because there is no degree of freedom about the za axis with two blades whereas there is with three blades.  Also, the  loads at the yaw bearing are somewhat greater for the two-bladed teetering hub in comparison to the three-bladed teetering hub.  This includes YawBrFyp, YawBrFzp, YawBrMxp.  A direct comparison of the two- and three-bladed AWT-27 teetering hubs is presented in the extensive modeling section.